1. Field of the Invention
The present invention relates to a one-chip microcomputer built-in system and, more particularly, to a one-chip microcomputer built-in system which uses a microcomputer incorporating a flash memory.
2. Description of the Related Art
Conventional flash memories have been described in detail in, for example, "Nikkei Microdevices" (Special report "Ready for magnetic disk replacement for flash DRAM, May 1992, pp. 25-62).
A technique associated with a one-chip microcomputer (to be abbreviated as a 1-.mu.COM hereinafter) incorporating a flash memory as a programming memory has already been presented by Hitachi as "H8/538F", and a technique for incorporating a flash memory in a 1-.mu.COM has already been known.
The "H8/538F" also has a write controller for rewriting the contents of the flash memory by a program. Additionally, a program is likely to be written in the flash memory in the microcomputer mounted in a product.
On the other hand, Jpn. Pat. Appln. KOKAI Publication No. 4-291489 discloses a technique in which a loader program ROM is incorporated in addition to a flash memory, and using a ROM program, a main control program is stored in the flash memory through a data communication device.
U.S. Pat. No. 4,423,934 discloses a technique in which a product is operated in predetermined conditions using a standard program, and a deviation from a standard value is obtained as a custom constant. Each product is programmed using this custom constant.
However, to rewrite the contents of a flash memory in a 1-.mu.COM mounted in the product, a hardware write controller is required to rewrite the flash memory by program control.
In addition, although the above-described Jpn. Pat. Appln. KOKAI Publication No. 4-291489 discloses a technique in which data is sequentially written in blocks of the flash memory, no technique for rewriting only a specific block is disclosed. No technique for writing an adjustment value for variations between products in the flash memory is disclosed.
According to the technique disclosed in U.S. Pat. No. 4,423,934, it is necessary to remove the emulator from a camera after programming and mount a programmed 1.mu.-COM (PROM) on the camera.
Furthermore, in the technique disclosed in Jpn. Pat. Appln. KOKAI Publication No. 4-291489, a program cannot be rewritten without a loader programming ROM after a 1-.mu.COM is mounted in a product.
On the other hand, Jpn. Pat. Appln. KOKAI Publication No. 4-170797 discloses a technique which allows to upgrade a program by using a 1-.mu.COM incorporating a flash memory while it is mounted in a product.
However, to rewrite the contents of the flash memory in the microcomputer while the 1-.mu.COM is mounted in a product, a hardware write controller is required to rewrite the flash memory by program control.
The above-mentioned Jpn. Pat. Appln. KOKAI Publication No. 4-170797 describes an updated circuit in a product. Although the upgraded circuit needs an appropriately upgraded program, there is no description of an upgraded program at all.